Frame.



J. L. RAWBON.

FRAME.

APPLICATION FILED JULY 20, 1911. 1,128,362, Patented Feb.16, 1915.

[I 1 Z ,9 i Z 52 6 4 7 9 6 IAHI/ 11" 2% 4 Um'rnn srarns rarnnr 0mm JOSEPH LOXTON RAWIBON, 0F TORONTO ONTARIO, CANADA.

FRAME.

To all whom it may concern:

Be it known that l, JOSEPH Lox'roN RAW- BoN, a subject of the King of England, re-

.siding at Toronto, county of York, Ontario, Canada, have invented a new and useful are often driven between the mortise and the tenon, wherefore upon the stretching of the canvas the tacks, yielding to the strain, give way, thus loosening the canvas, especially at the corners, and when the canvas 1s stretched it will tend to wrinkle, since thetransverse stretch and in canvas stretchers as ordinarily made two keys have been employed in the attempt to give the canvas the proper stretch in both directions. This, however, is far from satisfactory, since when one key is driven home, the other is often loosened and drops out. Again, there is no way of ascertaining when an equal tension in both directions has been brought about and the canvas is often stretched more one way than the other, thereby eventually causing the painting to crack.

In accordance with the present invention the joint is so constructed that the outer edges of the frame are solid to the miter and the tacks will therefore hold as well at the joint as elsewhere.

Morever, the present invention comprises a single key of novel construction for each joint, which will not only give equal expansion to the entire surface of the canvas, but the key will become locked in a manner'preventing it from subsequently loosening because of shrinkage of .the wood, or other causes, it being unnecessary to remove the key after having been once properly placed.

The invention will be best understood from a consideration of the following de- Serial No. 639,654.

tailed descriptiontaken in connection with the accompanying drawings forming a part of this specification.

In the drawings :Figure 1 is a plan view of a canvas stretcher frame constructed in accordance with the present invention with the wedges or keys in place ready to be driven in to cause the stretching of the canvas. Fig. 2 is a detail sectional view of one of the joints prior to the driving home of the wedge or key. Fig. 3 is a similar view showing the joint in an expanded andlocked position. Fig. 4 is a section on the line H of Fig. 3. Fig. 5 is a perspective view of the tongue end of a frame member and also showing the corresponding portion of the key groove. Fig. 6 is a perspective view of the matching or mortise joint member and the corresponding portion of the key groove. Fig. .7 is a perspective view of the key. Fig. 8 is a perspective view of a joint showing the solid or unbroken outer edges thereof. Fig. 9 is a sectional view-showing a modified form of mortise and tenon joint. Fig. 10 is a section on the line 10-10 of Fig. 9. r

Referring to the drawings, there is shown Specification of Letters Patent. Patented Feb. 16, 1915.

Application filed July 20, 1911.

a frame composed of side members 4 and end members 5, the side members being in the part cular 1 construction shown longer than the endmembers, although, of course,

the invention is not limited to frames of any particular shape, but, customarily canvas stretchers for .artists use are of oblong shape similar to the showing of Fig. 1. .The

frame members are mitered at the ends as indicated at 6, in accordance with the usual custom.

One end of each frame member isformed with a tenon 7. preferably midway between the outer faces of the member, with one edge 8 .of the face flush with the inner edge 9 of the corresponding member, while the end 10 of the tenon is cut at right angles to the edge 8 and at a point considerably short of the outer corner 11 of the miter. in the mitered end of the frame member just Formed described and immediately adjacent the tenon on one side thereof is a groove 12, of

which one face is composed of the corresponding face of the tenon 7, while the inner approximately at such point.

The correspondingend of'the matching member to theone just described is formed wallil3 of the groove tapers toward the edge '10 of the tenon merging into the miter wall with a mortise 14 shaped to receive the tenon 7. This mortise is provided with a wall 15 matching the edge 8 of the tenon and an end wall 16 corresponding to the end 10 of the tenon. in the same corresponding relation to the mortise 1 1 as the groove 12 is to the tenon 7, is' a corresponding groove 17 tapered like the groove 12 and when the two parts of the frame are placed together with the tenon 7 in the mortise 14:, the grooves 12 and 17 coact to form a tapered keyway.

Instead of forming the coacting ends of the frame members with an integral tenon and a mortise to receive the'same, theremay be provided a circular metallic tenon 18 shown in Figsr9 and 10 and a socket 19 of semi-circular shape is formed in the end of one of the members to receive one-half of the tenon, and the latter is held in the socket in any appropriate manner. The matching end member at the miter joint is provided. with a semicircular cut-out 20 to receive the tenon when the frame members are brought together. These two examples will indicate sufficiently that the invention is not limited to any particular form of blind joint in frames of this character, but any joint whereby tack room is provided will answer.

W hatever be the form of the mortise and tenon, and whether the tenon be formed integral with the corresponding frame member or separately therefrom, and whether it be angular, as shown in Fig. 5 or circular as shown in Fig. 9, or any other appropriate shape, there is provided a key 21 of wedge shape having formed along the wedge edges a suitable number of teeth 22.

Ordinarily the frames are made of comparatively soft wood, such as pine, or the like, while the wedges may be made of harder wood, or even of metal. The key is fiat in the particular construction shown and is adapted to the'wedge socket formed by the coacting grooves 12 and 17.

The frame members 4- and 5 are assembled into substantially the form shown in Fig. 1 and then the canvas is tacked to the frame in the ordinary manner, but since the outer edges of the frame are solid, neither the grooves nor the'mortise reaching to such outer edges, there is ample tacking space and tacks of any size'desirable may be used without danger of entering the mortise-or being driven into the tenon seated therein, and so preventing the subsequent expansion of the frame.

To tighten the canvas the wedges'or keys desired stretch to thecanvas; and since" the wedges act simultaneously upon both members of the frame at the joint, the canvas is stretched equally throughout, but because the longitudinal stretch of the canvas is greater than the transverse stretch, the end members will be moved bodily away from the side members to a greater extent than the side members are moved one from the other.

The comparatively soft wood of the frame yields more or less under the strain due to the stretching of the canvas which is made quite taut, and the teeth 22 sink to a greater or less extent into the end walls of the grooves 12 and 17. These teeth incline toward the base end of the wedge, so that their shoulders are presented toward such base end and consequently the teeth lock in the material of the frame members against movement of the wedge in the reverse direction to which it was moved in being driven into the frame to separate the joints thereof. The wedges, therefore, become self locking and cannot be removed short of destruction of the material of the wedge or of the frame, unless the canvas be first removed. The canvas stretcher, therefore, retains its permanent stretch despite any slight loosening of the parts due to shrinkage, for the wedges once driven home will retain their position indefinitely being positively locked by the teeth 22.

So far as the separation of the frame members at the joint is concerned, a wedge with plain sides will answer but the retention of the wedge is due solely to the frictional engagement of the sides of the wedge with the walls of the wedge or key socket, while with a wedge or key provided with marginal teeth the uncertainties of the frictional engagement are eliminated, and the wedge will hold its place despite shrinkage or other changes in the wood sufficient to loosen the plain wedge or key.

What is claimed is:

A; frame for stretching canvas, comprising side and end members mitered at the corners and there formed with respective tenon and mortise connections, the tenon and mortise at each joint being of less length in the direction of the length of the miter than said miter and stopping short of the outer end thereof to provide tacking room around the edges of the frame all the way to the outer ends of the miters and without interference with or by the tenons or mortises, said mitered ends of the members having matching grooves closely adjacent to the corresponding tenon and mortised portions with one wall of the corresponding groove for-med by'the tenon and said grooves tapering toward and terminating at the outer endsof the respective tenons and mortises, so as to in like manner stop short of 'the'outer ends of the miters, and fiat tapered keys adapted to the taper grooves and-actas my own, I have hereto aflixed my signa lpg to expand the frame {members to istretich ture in the presence of two Witnesses.

t 1e canvas eac tapered my being 0: equal thickness throughout with marginal teeth JOSEPH LOXTON O 5 or serrations of the same thickness as the Witnesses: I

key. HENRY JAMES CLIFFORD,

In testlmony, that I claim the foregoing s CHRISTINE ELIZABETH RAwBoN.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0. 

